1. Field of the Invention
The present invention relates to an endless belt mounted on an image forming apparatus, and, more particularly to a transfer belt unit for an image forming apparatus that controls an endless belt not to meander when the endless belt travels.
2. Description of the Related Art
In image forming apparatuses such as a multi function peripheral (MFP) and a printer of a tandem system, toner images of plural colors are transferred onto a transfer belt one after another to form a color toner image. In the tandem system, when the transfer belt meanders, an image quality of the color toner image is extremely deteriorated because of color drift. Therefore, there have been devices for correcting meandering of a transfer belt. As one of such devices, for example, Japanese Patent No. 2868879 discloses a belt driving device that tilts a steering roller, which switches a traveling direction of a transfer belt, according to a balance between an elastic force of a spring and torque of guide rollers on both sides of the steering roller.
However, since the elastic force of the spring is used for the movement of the steering roller, the device in the past is low in speed and reliability and is not suitable for mounting on high-performance and high-speed MFP and the like that are required to realize a high image quality.
Therefore, it is desired to develop a transfer belt unit for an image forming apparatus that can reset, when a transfer belt meanders, the transfer belt in a normal direction at high speed to thereby obtain a high-quality color image without color drift.